[Perf] support Eplb for deepseek v3

[ifromeast]

This PR is to integrate EPLB into vllm, not just map experts according to ranks.
we can get prior expert map as following:

1. Select a dataset to the model for inference, and count the frequency of all layers and all experts being selected, and get weight of shape [layers, experts].
2. use EPLB to got the global optimal expert map according to weight and GPUs, and get prior expert map of shape [layers, ranks, experts] by

phy2log, log2phy, logcnt = eplb.rebalance_experts(weight_matrix, num_replicas, num_groups, num_nodes, num_gpus)
phy2log = phy2log.view(layers, num_gpus, -1)  # [layers, gpu_ranks, expert_per_gpu]
e_maps = torch.full((layers, num_gpus, num_replicas), -1, dtype=torch.int32)
for l in range(layers):
    for r in range(num_gpus):
        e_ids = phy2log[l,r]
        e_maps[l, r, e_ids] = torch.arange(num_replicas // num_gpus, dtype=torch.int32)
torch.save(e_maps, 'expert_map.pth')

3. using the prior expert map to load MoE model by

vllm serve deepseek-ai/DeepSeek-V2-Lite-Chat -tp 8 --enable-expert-parallel --trust-remote-code --expert-map-path /path/to/expert_map.pth

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.

💬 Join our developer Slack at https://slack.vllm.ai to discuss your PR in #pr-reviews, coordinate on features in #feat- channels, or join special interest groups in #sig- channels.

Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can either: Add ready label to the PR or enable auto-merge.

🚀

[liweiqing1997]

Why did this job stop? Will it be restarted?

[abmfy]

Hi @liweiqing1997, I’m currently working on EPLB, please take a look at #18343